The proposed project is directed at understanding the cellular actions of estrogens and progestins in central neural tissue that mediate female sexual behavior. For several reasons, we have chosen the guinea pig as the animal in which to study this problem. In order to analyze neural effects of steroids we measure markers of steroid action such as induction of steroid receptors and polymerase activity. The characteristics of these markers (e.g. temporal specificity, chemical specificity and sex specificity) are then related to the expression of a particular aspect of female behavior, the lordosis response. Monoamine neurotransmitters modulate the expression of steroid-dependent female behaviors. Another object of this proposal is to identify the role of such transmitters by means of drug manipulation (e.g. administration of monoamine receptor agonists and antagonists, monoamine synthesis inhibitors). Particularly, the possibly that noradrenergic transmission facilitates, while dopaminergic transmission inhibits lordosis will be explored further. Finally, we will attempt to integrate findings on thh steroid-sensitive elements of the CNS with data on neurotransmitter modulation of female behavior. To accomplish this, we propose a series of experiments to demonstrate that noradrenergic transmission has a permissive effect on the induction of brain progestin-receptors by estrogen. If this relationship can be conclusively demonstrated, it will open the way to future work on steroid-transmitter interactions, and will provide a basis for understanding transmitter modulation of steroid-dependent activities of the central nervous system.